The present invention is directed at methods and compositions for coloring human and animal hair that do not require the use of chemical oxidants such as peroxides. The method utilizes electrochemical oxidation of certain organic oxidative dye precursors to generate reactive intermediates that can then participate in coupling reactions to form colored molecules capable of dying hair. Specifically, the method comprises applying to the hair an oxidative dye precursor mixture containing at least one primary intermediate and then contacting this mixture on the hair with an electrode system providing sufficient voltage to generate reactive intermediates through oxidation of the primary intermediate. The invention also relates to systems (or kits) that provide the means to accomplish these steps.
Permanent hair colorants commonly come in two parts: a dye solution and a developer solution. The developer solution is generally comprised of an oxidizing agent, typically hydrogen peroxide, and an alkaline buffering agent such as ammonia. In a conventional permanent hair coloring treatment, the dye solution and the developer solution are mixed and then applied to the hair, which is then left for about 25 min to about 45 minutes. The hair is then rinsed with water, treated with a post treatment conditioner, and then rinsed again with water.
The application of a dye solution in combination with an oxidant affords permanent hair coloring. However, as is well known, the repeated use of bleaching agents can damage the hair through indiscriminant oxidation. This is especially important for consumers who either have long hair or who frequently color their hair.
A second problem associated with conventional permanent hair coloring compositions and kits for use at home is inconvenience. Since permanent dyes are generated before they are applied to hair, there is the potential for staining the hands, and face during application and use. This requires gloves, and often masking of areas of the face.
The attainment of natural looking highlights, and tints is another problem encountered with conventional dyeing systems. Although many types of styling implements have been suggested in the art, it remains difficult for the average consumer to approach the aesthetic quality in terms of color nuances that have been heretofore only been available in a salon.
An additional problem associated with conventional dying systems is the convenient xe2x80x9cretouchingxe2x80x9d of the root areas between complete dying as the hair grows. It is often difficult to match the existing color which has changed to varying degrees and consequently consumers may be forced re-dye their hair before it is really necessary.
One objective of the present invention is a method of coloring the hair, especially gray hair that truly does not require a chemical oxidant.
Another objective of the invention is a convenient method of coloring hair that is less messy than conventional dyeing processes and that will provide a wider range of potential shades and tones from a limited set of chemical compositions.
An additional objective of the invention is a method of dyeing the hair that is capable of more easily generating natural looking highlights as well as providing a convenient and effective means of retouching the root area of hair so as to prolong the duration between hair colorings
A still further objective is to provide a convenient kit that can be used by individual consumers to practice at home the method described herein.
These and other objectives will become clear from the description of the invention.
The following patents and publications have been considered:
U.S. Pat. Nos. 5,472,456 and 5,569,368, respectively describe a method and system for electrophoretically applying therapeutic and cosmetic agents and dyes especially natural colorant such as melanin, to the hair.
Japanese Patent No. JP 6315410 A discloses a method of dyeing hair by flowing an electric current in an acidic hair dying agent coated on the hair until the agent is oxidized to color the hair. The preferred dyes are acidic inorganic compounds especially pyrogallol.
U.S. Pat. No. 5,072,746 discloses a hair grooming device for the electrocution of lice or other pests on the hair.
None of the references cited above teaches a method of applying to the hair an organic oxidative dye precursor mixture comprising a primary intermediate having a standard oxidation potential between 10 mV and 3 V; and subsequently contacting this mixture on the hair with an electrode system having sufficient voltage to directly form a reactive intermediate that generates an indo dye.
The subject invention provides a method for dyeing the hair by applying to the hair specific dye precursor compositions and then applying a means for electrochemically oxidizing these precursors to generate colored dye molecules that are substantive to the hair thus avoiding the use of chemical oxidants.
More specifically, the method for electrochemically dyeing the hair comprises carrying out the following steps in the order indicated:
i) applying to the hair an oxidative dye precursor mixture containing at least one primary intermediate having a standard Redox potential less than 1 volt,
ii) contacting the oxidative dye precursor mixture on the hair with an electrode system that provides sufficient voltage to electrochemically oxidize at least one of the primary intermediates to produce a reactive intermediate that generates colored dye through a coupling reaction with an oxidative dye precursor present in the mixture,
wherein the reactive intermediate is a quinone monoimine, a quinone diimine, a substituted quinone mono- a substituted quinone diimine, an indole imine, a substituted indole imine, or mixtures thereof.
A second embodiment of the invention is a system or kit that allows individual consumers to conveniently practice the disclosed electrochemical method of coloring the hair.
More specifically, the hair coloring system or kit comprises:
i) an oxidative dye precursor mixture containing at least one primary intermediate having a standard oxidation potential between 10 mV and 3 V,
iii) an electrode system that provides sufficient voltage to electrochemically oxidize at least one of the primary intermediates to produce a reactive intermediate that generates colored dye molecules through a coupling reaction with an oxidative dye precursor present in the mixture,
wherein the reactive intermediate is a quinone monoimine, a quinone diimine, a substituted quinone mono- a substituted quinone diimine, an indole imine, a substituted indole imine, or mixtures thereof.